Warmer world, longer hay fever: The rising tide of pollen
Climate change is causing an increase in the amount of pollen, leading to a rise in seasonal allergies. Experts warn about extreme allergic events that may become increasingly frequent.
Pollen is an essential element of our natural world. These microscopic particles travel between plants, usually from early spring to late summer, enabling their reproduction. Some pollen is spread by insects, while others are carried by the wind. Unfortunately, they cause allergies in sensitive individuals, which may now be intensifying even more. Scientists believe that rising global temperatures contribute to the extension of the pollen season, resulting in more pollen in the air.
Climate change will extend the pollen season by additional months
"We know that climate change is leading to greater amounts of pollen in the atmosphere. It's changing the seasonality of the pollen. It's changing the types of pollen that we're exposed to," says Paul Beggs from the BBC, a scientist at Macquarie University in Sydney. This phenomenon is especially noticeable in Europe, the United States, and Australia.
Researchers predict that pollen levels will be higher than the historical average in 39 US states this season. This means that people suffering from allergies may experience symptoms for a longer time. "The winter warms, the springs are starting earlier, and the falls are being delayed, and so the time that you spend outdoors in contact with allergic pollen is definitely going up," says Lewis Ziska from the BBC at Columbia University.
Scientists believe that without an immediate reduction in greenhouse gas emissions, the effect will likely worsen. Authors of scientific studies published in "Nature" (Y. Zhang, A. Steiner) estimated that by the year 2100, pollen seasons will begin up to 40 days earlier and end up to 15 days later than currently – potentially meaning an additional two months of symptoms for hay fever sufferers annually.
This is how carbon dioxide affects plants
This is partly due to rising levels of carbon dioxide (CO2) in the atmosphere, resulting from emissions from human activities. Many of the most troublesome plants for hay fever sufferers thrive on CO2.
The spread of invasive species to new parts of the world also triggers allergic reactions in new populations of people. In some parts of the world, including the US and Europe, one of the main culprits is ragweed (Ambrosia L), belonging to the aster family – a widely spread group of flowering plants that many consider weeds. There are various species of ragweed worldwide, but they can produce enormous amounts of pollen. A single plant can emit a billion grains of pollen. Ragweed grows in gardens and agricultural fields, but also in all kinds of urban nooks.
Ziska, author of the book "Greenhouse Planet" from 2022, conducted experiments with ragweed. "Every time we cranked up the carbon dioxide, the ragweed plants responded. They grew more. They produced more pollen," he told the BBC. He also added that he had "some evidence that they were producing a more allergenic form of the pollen, one that could induce your immune system to respond even to a greater extent than had been in the past."
Climate change has a significant impact on human health, and without coordinated efforts, the situation may worsen. "We have the studies now to show that it's really having an impact on human health," asserts a scientist from Macquarie University in Sydney.
